A Fast Locked-in Phase-Locked Loop Circuit Avoiding Cycle Skipping

Abstract

The invention discloses a fast locking phase-locked loop circuit avoiding cycle slip, which belongs to the technical field of integrated circuits. The fast locking phase-locked loop circuit includes: Voltage controlled oscillator, frequency divider. The frequency and phase detector, the charge pump, the intermediate stage circuit, the loop filter and the voltage-controlled oscillator are connected in sequence; the output OUT of the voltage-controlled oscillator is connected to the input IN of the frequency divider, and the frequency divider The output OUT terminal of the frequency discriminator is connected with the input IN terminal of the frequency and phase detector to form a feedback path. The present invention adjusts the initial output frequency of the VCO, thereby avoiding that when the loop is started, the output clock frequency of the VCO is too close to the expected frequency, that is, the reference clock frequency and the feedback clock frequency are too close, so that when the cycle slip occurs in the loop, the locked The time is greatly extended.

Description

technical field [0001] The invention belongs to the technical field of integrated circuits, and in particular relates to a fast-locked phase-locked loop circuit for avoiding cycle slips. Background technique [0002] Phase locked loop (PLL) is a frequency control system, which is widely used in circuit design, including clock generation, clock recovery, jitter and noise reduction, frequency synthesis and so on. The operation of the PLL is based on the phase difference between the reference clock signal and the feedback of the voltage-controlled oscillator (VCO) output clock signal. The cycle slip refers to that when the frequency of the feedback clock is lower than the frequency of the reference clock, it should be charged at this time, but because the phase of the reference clock lags behind the feedback clock, the charge pump discharges the loop filter instead. Or conversely, when the frequency of the feedback clock is greater than the frequency of the reference clock, it...

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Problems solved by technology

But this also increases the power consumption of the system to a certain extent and increases the complexity of the circuit.

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